3GPP (3rd Generation Partnership Project) is a project for discussing/creating specifications of a mobile communication system based on a network developed from W-CDMA (Wideband-Code Division Multiple Access) and GSM (Global System for Mobile Communications). The 3GPP has standardized the W-CDMA mode as a third-generation cellular mobile communication system and the service is sequentially started. HSDPA (High-Speed Downlink Packet Access) with higher communication speed has also been standardized and the service is started. The 3GPP is currently discussing about a mobile communication system (hereinafter referred to as “LTE-A (Long Term Evolution-Advanced)” or “Advanced-EUTRA”) that utilizes the development of the third generation radio access technology (hereinafter referred to as “LTE (Long Term Evolution)” or “EUTRA (Evolved Universal Terrestrial Radio Access)”) and a wider frequency band to realize faster data transmission/reception.
The OFDMA (Orthogonal Frequency Division Multiple Access) mode and the SC-FDMA (Single Carrier-Frequency Division Multiple Access) mode are modes using subcarriers orthogonal to each other to perform user-multiplexing and are discussed as communication modes in LTE. The OFDMA mode is a multi-carrier communication mode and is proposed for downlink, and the SC-FDMA mode is a single-carrier communication mode and is proposed for uplink.
On the other hand, for communication modes in LTE-A, it is discussed to introduce the OFDMA mode for downlink and the OFDMA mode and the Clustered-SC-FDMA (Clustered-Single Carrier-Frequency Division Multiple Access, also referred to as DFT-s-OFDM with Spectrum Division Control) mode for uplink in addition to the SC-FDMA mode. The SC-FDMA mode proposed as uplink communication mode in LTE and LTE-A are characterized in that PAPR (Peak to Average Power Ratio) at the time of transmission of data (information) can be suppressed to a lower level.
While a typical mobile communication system uses a continuous frequency band, it is discussed for LTE-A to use a plurality of continuous/discontinuous frequency bands (hereinafter, referred to as “carrier elements, carrier components (CC)” or “element carriers, component carriers (CC)”) in a multiple manner to implement operation as one frequency band (broad frequency band) (frequency band aggregation, also referred to as spectrum aggregation, carrier aggregation, and frequency aggregation). It is also proposed to give different frequency bandwidths to a frequency band used in downlink communication and a frequency band used in uplink communication so that the base station apparatus and the mobile station apparatus more flexibly use a wider frequency band to perform communication (asymmetric frequency band aggregation: asymmetric carrier aggregation) (Nonpatent Literature 1).
FIG. 9 is a diagram for explaining frequency band aggregation in a conventional technique. Giving the same bandwidth to a frequency band used in downlink (DL) communication and a frequency band used in uplink (UL) communication as depicted in FIG. 9 is also referred to as symmetric frequency band aggregation (symmetric carrier aggregation). As depicted in FIG. 9, the base station apparatus and the mobile station apparatus use the plurality of carrier components that are continuous/discontinuous frequency bands in a multiple manner, thereby performing communication in a wider frequency band constituted of the plurality of carrier components. Here, byway of example, it is depicted that a frequency band used in the downlink communication with a bandwidth of 100 MHz (hereinafter also referred to as DL system band or DL system bandwidth) is constituted of five carrier components (DCC1: Downlink Component Carrier 1, DCC2, DCC3, DCC4, and DCC5) each having a bandwidth of 20 MHz. By way of example, it is also depicted that a frequency band used in the uplink communication with a bandwidth of 100 MHz (hereinafter also referred to as UL system band or UL system bandwidth) is constituted of five carrier components (UCC1: Uplink Component Carrier 1, UCC2, UCC3, UCC4, and UCC5) each having a bandwidth of 20 MHz.
In FIG. 9, downlink channels such as a physical downlink control channel (hereinafter, PDCCH) and a physical downlink shared channel (hereinafter, PDSCH) are mapped on each of the downlink carrier components, and the base station apparatus uses the PDCCH to transmit, to the mobile station apparatus, the control information (such as resource allocation information, MCS (Modulation and Coding Scheme) information, and HARQ (Hybrid Automatic Repeat Request) process information) for transmitting a downlink transport block transmitted by using the PDSCH (i.e. uses the PDCCH to allocate the PDSCH to the mobile station apparatus), and uses the PDSCH to transmit the downlink transport block to the mobile station apparatus.
Also, uplink channels such as a physical uplink control channel (hereinafter, PUCCH) and a physical uplink shared channel (hereinafter, PUSCH) are mapped on each of the uplink carrier components, and the mobile station apparatus uses the PUCCH and/or the PUSCH mapped on each of the uplink carrier components to transmit, to the base station apparatus, the control signal (control information) of HARQ for the physical downlink control channel and/or the downlink transport blocks. The control signal (control information) of HARQ is a signal (information) indicative of ACK/NACK (Positive Acknowledgement/Negative Acknowledgement, ACK signal or NACK signal) and/or a signal (information) indicative of DTX (Discontinuous Transmission) for the physical downlink control channel and/or the downlink transport blocks. The signal indicative of DTX is a signal (information) indicating that the mobile station apparatus cannot detect the PDCCH from the base station apparatus. In FIG. 9, any of downlink/uplink channels such as the PDCCH, the PDSCH, the PUCCH, and the PUSCH may not be mapped on some downlink/uplink carrier components.
Similarly, FIG. 10 is a diagram for explaining asymmetric frequency band aggregation (asymmetric carrier aggregation) in a conventional technique. As depicted in FIG. 10, the base station apparatus and the mobile station apparatus give different bandwidths to a frequency band used in the downlink communication and a frequency band used in the uplink communication, and use the carrier components constitute these frequency bands in a multiple manner, thereby performing communication in a wider frequency band. Here, by way of example, it is depicted that a frequency band used in the downlink communication with a bandwidth of 100 MHz is constituted of five carrier components (DCC1, DCC2, DCC3, DCC4, and DCC5) each having a bandwidth of 20 MHz, and that a frequency band used in the uplink communication with a bandwidth of 40 MHz is constituted of two carrier components (UCC1 and UCC2) each having a bandwidth of 20 MHz. In FIG. 10, the downlink/uplink channels are mapped on each of the downlink/uplink carrier components, and the base station apparatus uses the PDSCHs to be allocated by the PDCCHs to transmit, to the mobile station apparatus, the downlink transport blocks in the same sub-frame, and the mobile station apparatus uses the PUSCH and/or the PUSCH to transmit, to the base station apparatus, the control signal of HARQ.
For the LTE-A, various methods have been proposed for the base station apparatus to employ when the base station apparatus executes allocation of the PDSCHs using the PDCCHs mapped on the downlink carrier components (Nonpatent Literature 2). FIG. 11 is a diagram for explaining one of the methods of allocating the PDSCHs using the PDCCHs in the conventional techniques. FIG. 11 depicts an enlarged portion of the downlink carrier components in FIG. 10 (a portion including DCC1, DCC2, and DCC3). As depicted in FIG. 11, the base station apparatus is able to allocate the plurality of PDSCHs using the plurality of PDCCHs mapped on a single downlink carrier component. FIG. 11 depicts the state as an example where the base station apparatus allocates the PDSCHs mapped on DCC1, DCC2, and DCC3 using three PDCCHs mapped on DCC2 (the PDCCHs each indicated by slant lines, grid lines, or net lines) (allocates the PDSCH of DCC1 using the PDCCH indicated by the slant lines, the PDSCH of DCC2 using the PDCCH indicated by the grid lines, and the PDSCH of DCC3 using the PDCCH indicated by the net lines). The base station apparatus is able to transmit to the mobile station apparatus (at most three) downlink transport block(s) in one same sub frame using the PDSCHs mapped on DCC1, DCC2, and DCC3.